Nokia NSE-3 SERIES, Service Manual

Page: 213 / 217

PAMS
Technical Documentation
NSE–3
Tuning Instructions
Page 11
Original 11/97
2. I/Q Modulator Amplitude Balance and Phase Shift Tuning
The purpose of this tuning operation is to adjust the I/Q modulator d.c. off-
sets and the I/Q modulator amplitude balance and phase shift.
I/Q modulator d.c. offsets, amplitude balance and phase shift tuning:
– Select Tuning –> TX I/Q...
– Select I/Q tuning values from PC’s memory, phone’s EEPROM or fac-
tory default values.
– Connect spectrum analyzer (with attenuator if needed) to phone an-
tenna connector.
– Check that TX power level is level 10, channel is 60 and TX data type
is 1.
– Adjust spectrum analyzer centre frequency to 902 MHz, Span 200
kHz, Res BW 10 kHz, Video BW 1 kHz and Sweep time 0.5 s.
–67.71 kHz +67.71 kHz
CHF
> 30 dB
> 35 dB
Set this value
to minimum
Amplitude &
phase difference:
Set this value
to minimum
D.C. offset
tunings:
– Select the ”TX I d.c. offset” option.
– Adjust the level of centre frequency (CHF signal) to minimum by vary-
ing D/A converter value with <– and –> buttons.
– The amplitude difference between CHF–67.7 kHz and CHF should be
>30 dB.
– Select option ”TX Q d.c. offset”.
– Adjust the level of signal CHF to minimum by varying D/A converter
value with
<–
and
–>
keys.